There are several well known types of electrical raceway systems which are designed to be placed in a floor. There are, for example, "underfloor" raceways as defined in Article 354 of the National Electrical Code and "cellular metal floor raceways" as defined in Article 356 of the National Electrical Code.
Service fittings designed for use with either of the two mentioned raceway systems typically sit on top of the duct or raceway, and thus the capacity of the service fitting is limited to the actual plan area of the service fitting times the concrete slab thickness over the raceway.
A typical example of an underfloor duct having a service fitting located on top of the duct is shown in U.S. Pat. No. 4,338,484 to Littrell.
An access unit placed on top of cellular metal flooring is shown in U.S. Pat. No. Re. 28,035 to Fork.
Additionally, in cellular metal flooring, access units are sometimes utilized which span a trough of the flooring and utilize the depth of the trough for additional capacity of the access unit. Typical examples are seen in U.S. Pat. No. 3,932,696 to Fork et al. and U.7S. Pat. No. 4,507,900 to Landis (see FIG. 7).
The prior art also includes trench ducts which utilize underfloor blind electrical terminal boxes as seen in U.S. Pat. No. 3,131,512 to MacLeod, Jr.
The prior art also includes independent conduit fed floor boxes such as those sold by Midland-Ross Corporation, Electrical Products Division, of Pittsburgh, Pa., under the trademark STEEL CITY.RTM..
Also, large capacity delivery modules are available for access type floors Such modules are marketed by Midland-Ross Corp., Electrical Products Division, of Pittsburgh, Pa., under the trademark MULT-A-CELL.RTM..
None of these designs, however, provide the capability in a typical underfloor duct system of providing a large capacity service fitting which is not limited to the depth of the slab thickness over the underfloor duct.